Illuminating unit having diffusion means

ABSTRACT

There is disclosed an image reading apparatus constructed by an illuminating unit for illuminating an object in a line shape, an image forming optical system for forming a light, as an image, from the object illuminated by the illuminating unit, a line sensor for converting the light formed as an image by the image forming optical system into an image signal, and a frame for holding the illuminating unit and the line sensor, wherein a shape in which vertices of at least a part of the cross section of the illuminating unit are connected by straight lines is set to a polygon of a pentagon or more, so that an image can be stably read at a high quality.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to an image reading apparatus for readingan object image and outputting an image signal.

[0003] 2. Related Background Art

[0004] Hitherto, as shown in a cross sectional view of FIG. 11, an imagesensor which is in contact with an original to be read and reads animage is constructed by: an image sensor board 2 on which a sensor IC 1is installed; a lens array 3 for guiding a reflected light from theoriginal illuminated by an illuminating unit 4 to the sensor IC 1; acover glass 5 which is come into contact with the original; and a frame6 for positioning and holding those component elements.

[0005] As an illuminating unit 4, a unit as shown in a cross sectionalview and a top view of FIG. 12 is used. The illuminating unit 4 isconstructed by: LEDs 7 of a lead frame type serving as light sourcesprovided on both ends; an optical guide member 8 arranged in alongitudinal direction for converting a light irradiated from the LEDsinto a line-shaped light; and a housing 9 having a square crosssectional shape for positioning and holding the LEDs 7 and optical guidemember 8. An electric power is supplied to the LED 7 from a power source(not shown) through a lead 11.

[0006] When such an illuminating unit 4 is attached to the frame, asshown in FIG. 11, in order to illuminate the light from the obliquedirection of 45° for the original, an attaching surface which isinclined by 45° for the original mounting surface is provided for theframe 6, and the surface corresponding to one side of a square in thecross section of the housing 9 constructing the illuminating unit 4 iscome into contact with the inclined attaching surface and is adhered byboth-side adhesive tape or the like, thereby positioning and fixing.

[0007] However, in the conventional image sensor mentioned above, sincethe housing of the illuminating unit having the square cross section isinstalled to the frame so as to be inclined by 45° for the originalsurface, there are the following problems.

[0008] (1) To enclose the illuminating unit into the frame, it isnecessary that a length of diagonal line in the cross section of thehousing of the illuminating unit is assured in the vertical direction inthe frame. However, the image sensor main body cannot be largely formed.Therefore, a thickness of frame with which the lower portion of theilluminating unit is come into contact has to be made thin. It isdifficult to work the frame. Even if the frame can be worked, amechanical strength of the frame is insufficient.

[0009] (2) An angle at which the illuminating unit is attached to theframe is not equal to 45° depending on an individual difference of eachimage sensor and an optical axis is deviated, so that there is a casewhere an illuminance on the original reading line doesn't reach aspecified value.

[0010] (3) To fix the illuminating unit to the frame, not only amaterial such as both-side adhesive tape or adhesive agent is necessarybut also a step of attaching such a material is added, so thatmanufacturing costs rise.

SUMMARY OF THE INVENTION

[0011] It is an object of the invention to enable an image to be read ata high quality.

[0012] Another object of the invention is to provide an image readingapparatus of a high mechanical strength.

[0013] Still another object of the invention is to miniaturize an imagereading apparatus.

[0014] Further another object of the invention is to suppress avariation in reading lines due to a deviation of an optical axis.

[0015] To accomplish the above objects, according to an embodiment ofthe invention, there is provided an image reading apparatus comprising:illuminating means for illuminating an object in a line shape; imageforming optical system for forming a light, as an image, from an objectilluminated by the illuminating means; a line sensor for converting thelight formed as an image by the image forming optical system into animage signal; and holding means for holding the illuminating means andthe line sensor, wherein a shape formed by connecting vertices in atleast a part of a cross section of the illuminating means by straightlines is set to a polygon of a pentagon or more.

[0016] According to another embodiment, there is provided an imagereading apparatus comprising: illuminating means which is constructed bya point light source and optical guide means for guiding and convertinga light from the point light source into a line-shaped light andilluminate an object in a line shape; an image forming optical systemfor forming the light, as an image, from the object illuminated by theilluminating means; a line sensor for converting the light formed as animage by the image forming optical system into an image signal; andholding means for holding the illuminating means and the line sensor,wherein at least a part of a cross section of the illuminating means hasa circular shape.

[0017] According to still another embodiment, there is provided an imagereading apparatus comprising: illuminating means for illuminating anobject in a line shape; an image forming optical system for forming thelight, as an image, from the object illuminated by the illuminatingmeans; a line sensor for converting the light formed as an image by theimage forming optical system into an image signal; and holding means forholding the illuminating means and the line sensor, wherein at least apart of the cross sectional shape of the illuminating means has acircular shape and a convex portion is formed on the outer periphery ofthe circular shape and is come into engagement with a concave portionformed in the holding means, thereby certainly positioning.

[0018] According to further another embodiment, there is provided animage reading apparatus comprising: illuminating means for illuminatingan object in a line shape; an image forming optical system for forming alight, as an image, from an object illuminated by the illuminatingmeans; a line sensor for converting the light formed as an image by theimage forming optical system into an image signal; and holding means forholding the illuminating means and the line sensor, wherein at least apart of the cross sectional shape of the illuminating means has acircular shape and a concave portion is formed on the outer periphery ofthe circular shape and is come into engagement with a convex portionformed in the holding means, thereby certainly positioning.

[0019] With the above construction, a cross sectional area of theilluminating means is small and an enough mechanical strength can beassured while miniaturizing the apparatus. Further, by certainlypositioning the illuminating means, a variation in reading line can besuppressed and an image can be read at a high quality.

[0020] The above and other objects and features of the present inventionwill become apparent from the following detailed description and theappended claims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a cross sectional view of an image sensor according tothe first embodiment;

[0022]FIG. 2 is a top view of an image sensor of the first embodiment;

[0023]FIG. 3 is a cross sectional view of an illuminating unit of thefirst embodiment;

[0024]FIG. 4 is a side elevational view of an illuminating unit of thefirst embodiment;

[0025]FIG. 5 is a detailed diagram of an optical guide member of thefirst embodiment;

[0026]FIG. 6 is a cross sectional view of an image sensor according tothe second embodiment;

[0027]FIG. 7 is a cross sectional view of an illuminating unit of thesecond embodiment;

[0028]FIG. 8 is a side elevational view of an illuminating unit of thesecond embodiment;

[0029]FIG. 9 is a cross sectional view of an image sensor according tothe second embodiment;

[0030]FIG. 10 is a cross sectional view of an image sensor according tothe second embodiment;

[0031]FIG. 11 is a cross sectional view of a conventional image sensor;and

[0032]FIG. 12 is a cross sectional view and a top view of a conventionalilluminating unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The first embodiment of the invention will now be describedhereinbelow with reference to FIGS. 1 to 5. FIG. 1 is a cross sectionalview of an image reading apparatus and FIG. 2 is a top view thereof.

[0034] The image reading apparatus according to the present embodimentis constructed by: the image sensor board 2 in which a plurality ofsensor ICs 1 each having a group of line-shaped photoelectric convertingelements (line sensors) are accurately arranged on a board made of aglass epoxy material or the like in correspondence to a length oforiginal to be read; the lens array 3 serving as an image formingoptical system; the illuminating unit 4 serving as illuminating means;the cover glass 5 serving as supporting means for supporting an originaland made of a light transmitting material; and the frame 6 serving asholding means and made of a material of a metal such as aluminum or thelike or a resin such as polycarbonate or the like for positioning andholding the above component elements.

[0035] The original supported by the cover glass 5 is illuminated by alight from the illuminating unit 4 from the oblique direction at anangle of 45°. The reflected light from the original is formed as animage onto the sensor IC 1 by the lens array 3. The sensor IC 1 convertslight information into an electric signal and transmits to a systemimage processing unit.

[0036]FIG. 3 is a cross sectional view of the illuminating unit 4 andFIG. 4 is a top view thereof.

[0037] As shown in FIGS. 3 and 4, the illuminating unit 4 is constructedby: the LEDs 7 serving as point light sources of the lead frame typeprovided as light sources at both ends; the optical guide member 8serving as optical guide means of a cylindrical shape and made of alight transmitting material such as an acrylic resin or the like inorder to guide the light of the LED in a line shape in the longitudinaldirection; and the housing 9 for positioning and holding the LEDs 7 andthe optical guide member 8. In the housing 9, a shape formed byconnecting vertices of a cross section by straight lines is a hexagon.

[0038] The LEDs 7 are provided on both ends of the optical guide member8 and the illumination light enters the optical guide member 8. Adiffusing surface 10 serving as a diffusing means is provided for theoptical guide member 8.

[0039] As shown in an enlarged diagram of FIG. 5, a fine tapered shapeof the diffusing surface 10 is continuously formed in the longitudinaldirection of the optical guide member 8. The light entering at an anglesuch that an incident angle θ to the tapered portion is equal to orlarger than 41° (in the case where the optical guide member is made ofan acrylic resin and a refractive index n=1.5) satisfies the totalreflection conditions and is emitted in a desired direction.

[0040] The housing 9 for positioning and holding the LEDs 7 and theoptical guide member 8 has a slit 12 for transmitting the light to oneside in the direction where the light of the hexagonal cross section isemitted. In order to gain a light amount, the outside of the opticalguide member has a white surface with a good light reflecting efficiencyand is made of a material such as an ABS resin or the like.

[0041] A method of manufacturing the image sensor will now be described.

[0042] The lens array 3 and illuminating unit 4 are inserted topredetermined positions of the frame 6, respectively. In theilluminating unit 4, three sides 9 a, 9 b, and 9 c of the hexagon of thehousing 9 shown in FIG. 3 are respectively come into contact with ahorizontal positioning surface 6 a and vertical positioning surfaces 6 band 6 c of the frame 6 shown in FIG. 1, thereby enabling the lightsource to be accurately positioned in the illuminating direction.

[0043] The cover glass 5 is adhered by an adhesive agent or the likeonto two surfaces 6 d and 6 e in the longitudinal direction of the frame6 set so as to sandwich the illuminating unit 4 and lens array 3 on aplane that is approximately the same as a top surface 9 d of the housing9 of the illuminating unit 4 inserted into the frame 6 and a top surfaceof the lens array 3.

[0044] The top surface 9 d of the housing 9 of the illuminating unit 4is a horizontal surface and is in contact with the surface of the coverglass 5 approximately in parallel, by adhering the frame 6 and coverglass 5, they can be fixed together with the illuminating unit 4. Byinserting the sensor array 2 into the frame 6 and fixing with anadhesive agent or the like, the apparatus is completed.

[0045] According to the embodiment as described above, since the shapein which the vertices of the cross section of the housing of theilluminating unit are connected by straight lines is a hexagon, thecross sectional area of the housing can be reduced and the frame of athickness with an enough mechanical strength can be assured. Further,since a sitting state of the illuminating unit to the frame is improved,a deviation of the optical axis can be prevented and a variation inilluminances of the original reading lines among the products can besuppressed. By adhering the frame and the cover glass, the illuminatingunit can be also simultaneously fixed. The assembling steps can besimplified and the costs can be reduced.

[0046] Although the embodiment has been shown and described with respectto the example in the case where the shape in which the vertices of thecross section of the housing of the illuminating unit are connected bystraight lines is a hexagon, the invention is not limited to such anexample. By setting such a shape to a polygon of a pentagon or more, asimilar effect can be obtained.

[0047]FIGS. 6, 7, and 8 show an image reading apparatus of the secondembodiment. Since a construction of the image reading apparatus of thesecond embodiment is fundamentally similar to that of the firstembodiment, the description of the same portions is omitted here.

[0048] The optical guide member 8 in the embodiment has a cylindrical orelliptic cylindrical shape or a shape similar thereto. In order tominimize a volume of illuminating unit 4, it is desirable that a crosssectional shape of the housing 9 has a circular or an elliptic shape ora shape similar thereto in correspondence to the optical guide member 8.On the other hand, when the shape of the housing 9 is set to a simplecylindrical or elliptic cylindrical shape, when it is attached to theframe 6, the position in the optical axial direction is not determined.

[0049] In the embodiment, therefore, although the housing 9 has acylindrical shape, convex portions 13 are formed on both ends of thehousing 9. Concave portions 14 are formed in the frame 6 so that theconvex portions 13 are fitted into the concave portions 14. By insertingthe convex portions 13 into the concave portions 14, the position in theoptical axial direction and the position in the longitudinal directioncan be simultaneously determined. With respect to the foregoing firstembodiment as well, by forming the convex portions 13 in the housing 9and by inserting the convex portions 13 into the concave portions 14 ofthe frame 6 as shown in FIG. 9 in a manner similar to the secondembodiment, the positioning in the longitudinal direction can becertainly executed. In the embodiment, although the convex portions havebeen formed in the housing, by forming convex portions 15 in the frameand forming concave portions 16 in the housing as shown in FIG. 10, asimilar effect is derived.

[0050] Further, although the shape of the equal magnification opticalsystem has been described in the above embodiments, the invention can bealso obviously applied to the image sensor using a reductionmagnification optical system.

[0051] Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

What is claimed is:
 1. An image reading apparatus comprising: (A)illuminating means for illuminating an object in a line shape; (B) animage forming optical system for forming a light, as an image, from theobject illuminated by said illuminating means; (C) a line sensor forconverting the light formed as an image by said image forming opticalsystem into an image signal; and (D) holding means for holding saidilluminating means and said line sensor, wherein a shape in whichvertices in at least a part of a cross section of said illuminatingmeans are connected by straight lines is a polygon of a pentagon ormore.
 2. An apparatus according to claim 1, wherein at least three sidesof said illuminating means and said holding means are come into contactwith each other, thereby positioning said illuminating means.
 3. Anapparatus according to claim 1, wherein said illuminating means includesa point light source and optical guide means for guiding the light fromsaid point light source and converting said light into a line-shapedlight.
 4. An apparatus according to claim 3, wherein said illuminatingmeans further includes diffusing means for illuminating the lightconverted in the line-shaped light by said optical guide means in apredetermined direction.
 5. An apparatus according to claim 4, whereinsaid diffusing means has a stairway-shaped diffusing surface.
 6. Anapparatus according to claim 3, wherein said illuminating means furtherincludes a housing for holding said point light source and said opticalguide means.
 7. An apparatus according to claim 6, wherein said housinghas a slit in the illuminating direction of the light.
 8. An apparatusaccording to claim 1, further comprising supporting means for supportingsaid object, and wherein by adhering a lower surface of said supportingmeans onto a top surface of said holding means, said illuminating meansis fixed.
 9. An apparatus according to claim 8, wherein said supportingmeans is a light transmitting member.
 10. An image reading apparatuscomprising: (A) illuminating means which is constructed by a point lightsource and optical guide means for guiding and converting a light fromsaid point light source into a line-shaped light and illuminates anobject in a line shape; (B) an image forming optical system for formingthe light, as an image, from the object illuminated by said illuminatingmeans; (C) a line sensor for converting the light formed as an image bysaid image forming optical system into an image signal; and (D) holdingmeans for holding said illuminating means and said line sensor, whereinat least a part of a cross sectional shape of said illuminating means isa circular shape.
 11. An apparatus according to claim 10, wherein saidilluminating means further includes diffusing means for illuminating thelight converted in the line-shaped light by said optical guide means ina predetermined direction.
 12. An apparatus according to claim 11,wherein said diffusing means has a stairway-shaped diffusing surface.13. An apparatus according to claim 11, wherein said illuminating meansfurther includes a housing for holding said point light source and saidoptical guide means.
 14. An apparatus according to claim 13, whereinsaid housing has a slit in the illuminating direction of the light. 15.An apparatus according to claim 10, further comprising supporting meansfor supporting said object, and wherein by adhering a lower surface ofsaid supporting means onto a top surface of said holding means, saidilluminating means is fixed.
 16. An apparatus according to claim 15,wherein said supporting means is a light transmitting member.
 17. Anapparatus according to claim 10, wherein at least a part of a crosssectional shape of said illuminating means is an elliptic shape.
 18. Animage reading apparatus comprising: (A) illuminating means forilluminating an object in a line shape; (B) an image forming opticalsystem for forming a light, as an image, from the object illuminated bysaid illuminating means; (C) a line sensor for converting the lightformed as an image by said image forming optical system into an imagesignal; (D) holding means for holding said illuminating means and saidline sensor, wherein at least a part of a cross sectional shape of saidilluminating means is a circular shape and a convex portion is formed onan outer periphery of said circular shape and is come into engagementwith a concave portion formed in said holding means, thereby certainlypositioning.
 19. An apparatus according to claim 18, wherein saidilluminating means further includes diffusing means for illuminating thelight converted in the line-shaped light by said optical guide means ina predetermined direction.
 20. An apparatus according to claim 19,wherein said diffusing means includes a stairway-shaped diffusingsurface.
 21. An apparatus according to claim 19, wherein saidilluminating means further includes a housing for holding said pointlight source and said optical guide means.
 22. An apparatus according toclaim 21, wherein said housing has a slit in the illuminating directionof the light.
 23. An apparatus according to claim 18, further comprisingsupporting means for supporting said object, and wherein by adhering alower surface of said supporting means onto a top surface of saidholding means, said illuminating means is fixed.
 24. An apparatusaccording to claim 23, wherein said supporting means is a lighttransmitting member.
 25. An apparatus according to claim 18, wherein atleast a part of a cross sectional shape of said illuminating means is anelliptic shape.
 26. An image reading apparatus comprising: (A)illuminating means for illuminating an object in a line shape; (B) animage forming optical system for forming a light, as an image, from theobject illuminated by said illuminating means; (C) a line sensor forconverting the light formed as an image by said image forming opticalsystem into an image signal; (D) holding means for holding saidilluminating means and said line sensor, wherein at least a part of across sectional shape of said illuminating means is a circular shape anda concave portion is formed on an outer periphery of said circular shapeand is come into engagement with a convex portion formed in said holdingmeans, thereby certainly positioning.
 27. An apparatus according toclaim 26, wherein said illuminating means further includes diffusingmeans for illuminating the light converted in the line-shaped light bysaid optical guide means in a predetermined direction.
 28. An apparatusaccording to claim 27, wherein said diffusing means has astairway-shaped diffusing surface.
 29. An apparatus according to claim27, wherein said illuminating means further includes a housing forholding said point light source and said optical guide means.
 30. Anapparatus according to claim 29, wherein said housing has a slit in theilluminating direction of the light.
 31. An apparatus according to claim26, further having supporting means for supporting said object, andwherein by adhering a lower surface of said supporting means onto a topsurface of said holding means, said illuminating means is fixed.
 32. Anapparatus according to claim 31, wherein said supporting means is alight transmitting member.
 33. An apparatus according to claim 26,wherein at least a part of a cross sectional shape of said illuminatingmeans is an elliptic shape.